Theoretical Prediction and Classification of Topological Semimetals

日期:2018-05-28 阅读:607


Discovering new phases of matter and finding new materials are everlasting tasks in material science. From the first usage of stone to the wide applications of semiconductors, the espial of new materials is always playing a crucial role in human history. Nowadays, the discovery of topological materials may open a new era of condensed matter physics. Since the discovery of the first Weyl semimetal in TaAs family [1,2], new topological semimetals have caught intensive research interests in both theory and experiment. In this talk, we first show recent experimental advances of topological semimetals. Later we present our new theories of topological metals. In nonmagnetic chiral crystals, we determined that all point-like nodal degeneracies with relevant SOC carry nontrivial Chern numbers [3-5]. In the crystals with perpendicular crystalline mirror planes, we proposed the new 3D band crossings characterized by nontrivial links such as a Hopf link or a coupled-chain[6].

[1]S-Y Xu, et. al., Discovery of a Weyl Fermion semimetal and topological Fermi arcs, Science 349, 613-617 (2015)

[2]B.Q. Lv, et. al.,Experimental Discovery of Weyl semimetal TaAs, Phys. Rev. X 5, 031013 (2015)

[3]G. Chang, et. al., Universal Topological Electronic Properties of  Nonmagnetic Chiral Crystals, Preprint at (2016)

[4]G. Chang, et. al., Unconventional chiral fermions and large topological Fermi arcs in RhSi, Phys. Rev. Lett. 119, 206401 (2017)

[5]P. Tang, et. al., multiple types of topological fermions in transition metal silicides, Phys. Rev. Lett. 119, 206402 (2017)

[6]G. Chang, et. al., Topological Hopf-link and Chain link semimetal states and their application to Co2MnGa, Phys. Rev. Lett.  119, 156401 (2017)  (Editors’ Sugesstions)


2018.05 ~ Postdoctoral Research Associate, Department of Physics, Princeton University, Advisor: Prof. M. Zahid Hasan

2017.10 ~ 2018.05: Postdtoral Research Associate, Institute of Physics, Academica Sinica,

2014.01 ~ 2017.10:  Ph.D in Physics, National University of Singapore, Singapore. Thesis: Theoretical Prediction and Classification of Topological Metals:  Weyl Semimetals and Beyond. Advisor: Prof. Hsin Lin

2012.08 ~2013.07: M.S. in Physics, National University of Singapore, Singapore.

2008.09 ~2012.06: B.S. in Physics, Soochow University, China.


I am working on varies topological phases in condensed matter physics, such as topological semimetals and topological insulators. Using first-principles calculations and other advanced computational techniques, I have predicted several Weyl semimetals: the TaAs class, the LaAlGe family, W1-xMoxTe2, Ta3S2, Co2TiX, and SrSi2. Among them, the TaAs class was the first experimentally confirmed Weyl semimetals and in the LaAlGe family, the type-II Weyl fermions were first observed.Besides searching for new materials, I am also working on classifying new topology phases. I have found the universal topological electronic property in chiral crystals. I have also classified a new threefold nexus fermion and defined the Hopf-link semimetal phase for the first time. I have also proposed a fourfold spin 3/2 chiral fermion in condensed matter physic for the first time, which is closely related but different from Rarita–Schwinger fermions in high-energy physics.My research involves extensive and close collaborations with many distinguished experimental groups. I have many experiences in analyzing data from angle-resolved photoemission (ARPES), and scanning tunneling spectroscopy (STM). My theoretical calculations of bulk electronic structures, surface states, quasiparticle interference patterns, and so on are always offering crucial and timely support for experimental measurements of my collaborators.


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